Reviews should be about the game though. Everyone is entitled to their opinion, that's fair, but development time should not be weighted in on a review of how good a game is. Like you said so yourself. When this game is done and there is no longer a wait time between updates, he's not going to come back here and change his score to reflect that. He's putting it into consideration here and now on how his final score is weighted.
If he wants to think the characters are shallow or flat or unoriginal, that's fine. Different wordings, same meanings. He can say that part as that's what really should be in reviews and what players looking at reviews look for when they want real opinions on the game. The reviews total score should not be considered with development time in mind though. Especially when he doesn't understand what goes into development.